Titanium phosphate powder, production method therefor, and white pigment for cosmetics

ABSTRACT

The titanium phosphate powder of the present invention includes plate-shaped crystalline particles of titanium phosphate, an average thickness of the plate-shaped crystalline particles is 0.01 μm or more and less than 0.10 μm, and an aspect ratio, which is a value obtained by dividing an average primary particle diameter of the plate-shaped crystalline particles by the average thickness, is 5 or more. In the method for producing a titanium phosphate powder of the present invention, a raw material containing titanium and phosphorus is caused to react by a hydrothermal synthesis method, and when the titanium phosphate powder including plate-shaped crystalline particles of titanium phosphate is produced, a mixture of titanium sulfate and phosphoric acid is used as the raw material.

TECHNICAL FIELD

The present invention relates to a titanium phosphate powder, aproduction method therefor, and a white pigment for cosmetics.

BACKGROUND ART

As a titanium phosphate powder, one composed of amorphous titaniumphosphate (for example, see PTL 1) and one composed of plate-shapedcrystalline particles of titanium phosphate (for example, see PTL 2) aredisclosed.

PTL 1 describes the use of, as an ultraviolet blocking agent, amorphousphosphate of Ce and/or Ti, containing one or more elements of B, Al, Si,Zn, Ga, Zr, Nb, Mo, Ta, and W as a crystallization inhibiting component.PTL 1 further describes that the ultraviolet blocking agent is amorphousphosphate having excellent heat resistance, and suitable applications ofthe ultraviolet blocking agent include a cosmetic product, a resinmolded article, a paint, and the like.

PTL 2 describes a method of producing a titanium phosphate powdercomposed of plate-shaped crystalline particles of titanium phosphate bycausing a raw material containing titanium and phosphorus to react by ahydrothermal synthesis method. PTL 2 further describes that plate-shapedcrystalline particles of titanium phosphate, corresponding to thestructural formula of Ti(HPO₄)₂.H₂O are obtained by this method.

As a specific example, PTL 2 describes that hexagonal plate-shapedcrystalline particles of titanium phosphate, having a particle diameterof 0.25 to 0.5 μm and 0.4 to 0.7 μm and a thickness of 0. 1 to 0. 2 μmare obtained. PTL 2 further describes that the obtained plate-shapedcrystalline particles of titanium phosphate are useful as a reinforcingagent of a building material, a pigment of a paint, and the like.

PTL 2 does not describe an example of using a mixture of titaniumsulfate and phosphoric acid as a raw material in the method forproducing a titanium phosphate powder composed of plate-shapedcrystalline particles of titanium phosphate.

CITATION LIST Patent Literatures

PTL 1: JP 4649102 B2

PTL 2: JP S49-1720 A

SUMMARY OF INVENTION Technical Problem

As mentioned above, in the case where the powder is an additive, apigment, or the like which is used by adding it to cosmetics, a paint,and the like, each of particles constituting the powder preferably has athin plate shape because slipperiness among particles becomes favorable.

However, the method described in PTL 2 is susceptible to improvement interms of obtaining a powder suitable for applications such as additivesand pigments.

An object of the present invention is to provide a powder suitable forapplications such as additives and pigments.

Solution to Problem

The titanium phosphate powder according to one aspect of the presentinvention is a titanium phosphate powder that includes plate-shapedcrystalline particles of titanium phosphate, wherein an averagethickness of the plate-shaped crystalline particles is 0.01 μm or moreand less than 0.10 μm, and an aspect ratio that is a value obtained bydividing an average primary particle diameter of the plate-shapedcrystalline particles by the average thickness is 5 or more.

The method for producing a titanium phosphate powder according to oneaspect of the present invention is a method for producing a titaniumphosphate powder including plate-shaped crystalline particles oftitanium phosphate, the method including causing a raw materialcontaining titanium and phosphorus to react by a hydrothermal synthesismethod, wherein the raw material is a mixture of titanium sulfate andphosphoric acid.

Advantageous Effects of Invention

The titanium phosphate powder of the present invention can be suitablyused as an additive, a pigment, or the like.

According to the method for producing a titanium phosphate powder of thepresent invention, a powder suitable for applications such as additivesand pigments can be obtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a graph illustrating a relationship between the concentrationof phosphorus in a mixture of titanium(IV) sulfate and phosphoric acidand the average thickness of hexagonal plate-shaped crystallineparticles of titanium phosphate, obtained from the results of ProductionExamples 1 to 10.

FIG. 2 is a graph illustrating a relationship between the concentrationof phosphorus in a mixture of titanium(IV) sulfate and phosphoric acidand the average primary particle diameter of hexagonal plate-shapedcrystalline particles of titanium phosphate, obtained from the resultsof Production Examples 1 to 10.

FIG. 3 is a graph illustrating a relationship between the averagethickness and the average primary particle diameter of hexagonalplate-shaped crystalline particles of titanium phosphate, obtained fromthe results of Production Examples 1 to 10.

FIG. 4 is a graph illustrating a relationship between the averageprimary particle diameter and the aspect ratio of hexagonal plate-shapedcrystalline particles of titanium phosphate, obtained from the resultsof Production Examples 1 to 10.

FIG. 5 is a graph illustrating a relationship between the concentrationof titanium in a mixture of titanium(IV) sulfate and phosphoric acid andthe average primary particle diameter of hexagonal plate-shapedcrystalline particles of titanium phosphate, obtained from a productionexperiment.

FIG. 6 is an SEM image of a titanium phosphate powder of ProductionExample 2.

FIG. 7 is an SEM image of a titanium phosphate powder of ProductionExample 11.

DESCRIPTION OF EMBODIMENT

An embodiment of the present invention will be described in detailbelow. The following embodiment merely shows an example of the presentinvention, and the present invention is not limited to the presentembodiment. Various variations and modifications can be made to thefollowing embodiment, and embodiments with such variations andmodifications can be included in the scope of the present invention.

The titanium phosphate powder according to the present embodimentincludes plate-shaped crystalline particles of titanium phosphate. Theaverage thickness of the plate-shaped crystalline particles is 0.01 μmor more and less than 0.10 μm, and an aspect ratio, which is a valueobtained by dividing the average primary particle diameter of theplate-shaped crystalline particles by the average thickness, is 5 ormore.

An average primary particle diameter of the plate-shaped crystallineparticles of titanium phosphate is not particularly limited and can be0.05 μm or more and 1.5 μm or less. The plate-shaped crystallineparticles of titanium phosphate may be hexagonal plate-shapedcrystalline particles.

The titanium phosphate powder according to the present embodiment is atitanium phosphate powder including thin plate-shaped crystallineparticles having a high aspect ratio, which is a value obtained bydividing the particle diameter by the thickness, and a thickness of lessthan 0.1 μm (i.e., particles of titanium phosphate each having a shapecontrolled to be a thin plate shape). Thus, slipperiness among particlesof titanium phosphate is favorable. Therefore, the titanium phosphatepowder according to the present embodiment is suitable as an additiveadded to a cosmetic agent such as a sunscreen cosmetic agent or apigment added to a paint. The titanium phosphate powder according to thepresent embodiment is also suitable as a white pigment for cosmetics.

The titanium phosphate powder according to the present embodiment can beproduced by causing a raw material containing titanium and phosphorus toreact by a hydrothermal synthesis method. This raw material is a mixtureof titanium sulfate (Ti(SO₄)₂) and phosphoric acid (H₃PO₄). The use oftitanium sulfate as a titanium source facilitates the formation of thinplate-shaped crystalline particles of titanium phosphate having a higheraspect ratio.

The reaction conditions of the hydrothermal synthesis method are notparticularly limited. However, the reaction temperature can be 100° C.or more and 160° C. or less. When the reaction temperature is 160° C. orless, a reaction vessel made of a glass lining material can be used inproduction of titanium phosphate powder, and the titanium phosphatepowder can be produced by a general-purpose facility. Thus, theproduction cost can be reduced.

When the reaction temperature is 160° C. or less, the titanium phosphatepowder can be produced in a first-class pressure vessel (pressure: 1 MPaor less). Further, when the temperature is 160° C. or less, the chemicalconcentration in production of titanium phosphate powder can be setunder a wider range of conditions. On the other hand, when the reactiontemperature is 100° C. or more, highly-crystalline plate-shapedcrystalline particles of titanium phosphate can be easily obtained, andfurther, the titanium phosphate powder can be produced by a simpleproduction facility because the viscosity of the product is low.

If the reaction temperature is 100° C. or less, the crystallinity of theplate-shaped crystalline particles of titanium phosphate may be slightlyreduced, and the viscosity of the product may be slightly increased,which may affect the design of the production facility. Therefore, it ismore preferable that the reaction temperature be 110° C. or more and160° C. or less. In the reaction temperature range of 100° C. or moreand 160° C. or less, there is no significant difference in thecrystallinity of the plate-shaped crystalline particles of titaniumphosphate.

The ratio [P]/[Ti] of the concentration [P] of phosphorus by mole to theconcentration [Ti] of titanium by mole in the raw material may be 3 ormore and 21 or less. When the ratio [P]/[Ti] is 3 or more, preferably 5or more, plate-shaped crystalline particles of titanium phosphate areeasily generated. On the other hand, in the case where the concentrationof titanium in the raw material is the same, the larger the ratio[P]/[Ti] is, the smaller the average primary particle diameter of theplate-shaped crystalline particles of titanium phosphate tends to be,but even if the ratio [P]/[Ti] exceeds 21, further reduction in averageprimary particle diameter does not occur, and the average primaryparticle diameter is almost constant.

The concentration of titanium in the raw material may be 0.05 mol/L ormore and 1.0 mol/L or less. When the ratio [P]/[Ti] is the same, thehigher the concentration of titanium in the raw material is, the smallerthe average primary particle diameter and the average secondary particlediameter of the plate-shaped crystalline particles of titanium phosphatetend to be. Further, by increasing the concentration of titanium in theraw material, the production cost can be reduced. Therefore, theconcentration of titanium in the raw material is preferably 0.05 mol/Lor more, more preferably 0.2 mol/L or more. However, if theconcentration of titanium in the raw material is too high, the viscosityof the product may increase, and the uniformity of the product maydecrease, so that the concentration of titanium in the raw material ispreferably 1.0 mol/L or less, more preferably 0.6 mol/L or less.

Production Examples

The present invention will be described in further detail below withreference to production examples of the titanium phosphate powder shownbelow.

Production Examples 1 to 11 shown in Table 1 are examples where titaniumphosphate powders each including hexagonal plate-shaped crystallineparticles of titanium phosphate were produced by causing titanium(IV)sulfate and phosphoric acid to react with each other by a hydrothermalsynthesis method.

The hydrothermal synthesis method is described in detail. First,titanium(IV) sulfate as a titanium source and phosphoric acid as aphosphorus source were mixed to obtain a mixture, and the mixture wasthen heated at a predetermined temperature to cause hydrothermalsynthesis. The pressurization at this time was natural pressurization.The concentration of titanium in the mixture of titanium(IV) sulfate andphosphoric acid was 0.2 mol/L or more and 0.6 mol/L or less. After thereaction was performed fora predetermined period of time, a slurry-likeproduct was cooled and cleaned with water to obtain a titanium phosphatepowder.

TABLE 1 Average primary Concentration Concentration ConcentrationReaction Reaction particle Average Prod. of titanium of phosphorousratio temperature time diameter thickness Aspect Ex. (mol/L) (mol/L)([P]/[Ti]) (° C.) (h) (μm) (μm) ratio 1 0.30 3.96 13 160 5 0.35 0.048 72 0.30 3.96 13 110 5 0.24 0.017 14 3 0.30 3.96 13 100 5 0.21 0.019 11 40.22 3.27 15 160 5 1.33 0.099 13 5 0.22 4.55 21 160 5 0.24 0.026 9 60.26 4.29 17 130 5 0.19 0.025 8 7 0.39 5.24 13 110 5 0.12 0.014 9 8 0.456.08 14 110 5 0.078 0.012 7 9 0.58 7.75 13 110 5 0.072 0.014 5 10 0.603.32 6 110 5 0.886 0.084 11 11 0.60 2.58 4 110 5 — — —

The concentration of titanium (by mole) [Ti] and the concentration ofphosphorus (by mole) [P] in each mixture of titanium(IV) sulfate andphosphoric acid and each concentration ratio [P]/[Ti] are as shown inTable 1. Each reaction temperature and each reaction time in thehydrothermal synthesis method are also shown in Table 1.

The average primary particle diameter and the average thickness of eachof the obtained titanium phosphate powders of Production Examples 1 to11 were measured, and the aspect ratio was calculated from thesenumerical values. The average primary particle diameter was obtained byanalyzing an image obtained by a scanning electron microscope using animage analysis software Mac-View ver. 4 manufactured by MOUNTECH Co.Ltd. Table 1 summarizes the results obtained.

A relationship between the concentration of phosphorus in the mixture oftitanium(IV) sulfate and phosphoric acid and the average thickness ofhexagonal plate-shaped crystalline particles of titanium phosphate,obtained from the results of Production Examples 1 to 10, is shown inthe graph of FIG. 1. A relationship between the concentration ofphosphorus in a mixture of titanium(IV) sulfate and phosphoric acid andthe average primary particle diameter of hexagonal plate-shapedcrystalline particles of titanium phosphate, obtained from theseresults, is shown in the graph of FIG. 2. A relationship between theaverage thickness and the average primary particle diameter of hexagonalplate-shaped crystalline particles of titanium phosphate, obtained fromthe results shown in Table 1, is shown in the graph of FIG. 3. Arelationship between the average primary particle diameter and theaspect ratio of hexagonal plate-shaped crystalline particles of titaniumphosphate, obtained from the results shown in Table 1, is shown in thegraph of FIG. 4.

(Concentration of Titanium)

Each titanium phosphate powder was produced by a hydrothermal synthesismethod under the conditions where the concentration ratio [P]/[Ti] wasconstant (16.5) and the concentration of titanium was 0.22 mol/L or 0.26mol/L. The reaction temperature was 110° C., 120° C., 130° C., or 160°C.

The results demonstrate that the higher the concentration of titaniumis, the smaller the average primary particle diameter of theplate-shaped crystalline particles of titanium phosphate is.

Subsequently, each titanium phosphate powder was produced by ahydrothermal synthesis method under the conditions where theconcentration ratio [P]/[Ti] was constant (13.4) and the concentrationof titanium was 0.39 mol/L, 0.45 mol/L, 0.52 mol/L, or 0.58 mol/L. Thereaction temperature was set to be constant (110° C.)

The results demonstrate that the higher the concentration of titaniumis, the lower the production cost is. A relationship between theconcentration of titanium and the average primary particle diameter ofthe obtained plate-shaped crystalline particles of titanium phosphate isshown in the graph of FIG. 5. As can be seen from this graph, the higherthe concentration of titanium is, the smaller the average primaryparticle diameter of the plate-shaped crystalline particles of titaniumphosphate is.

These results demonstrate that the average primary particle diameter ofthe plate-shaped crystalline particles of titanium phosphate can becontrolled to a desired size by reducing the concentration of phosphorusand increasing the concentration of titanium.

(Concentration of Phosphorus)

The effect of the concentration of phosphorus in the case where theconcentration of titanium is high (e.g., 0.4 mol/L or more) wasexamined. Each titanium phosphate powder was produced by a hydrothermalsynthesis method under the conditions where the concentration oftitanium was 0.22 mol/L, 0.41 mol/L, or 0.60 mol/L and the concentrationratio [P]/[Ti] and the concentration of phosphorus were changedvariously. The reaction temperature was 160° C. when the concentrationof titanium was 0.22 mol/L, and the reaction temperature was 110° C.when the concentration of titanium was 0.41 mol/L and 0.60 mol/L.

As a result, at any concentration of titanium, when the concentration ofphosphorus was 2.6 mol/L or less, the crystallinity of titaniumphosphate was reduced, and plate-shaped crystalline particles were notformed, but when the concentration of phosphorus was 3.3 mol/L or more,the plate-shaped crystalline particles of titanium phosphate wereformed. Similar to the case where the concentration of titanium was low(e.g., 0.2 mol/L), the average primary particle diameter of plate-shapedcrystalline particles of titanium phosphate tended to be smaller as theconcentration of phosphorus was higher.

In addition, the results of the examination under the conditions wherethe concentration of titanium was constant (0.60 mol/L) and theconcentration of phosphorus was changed variously (3.3, 4.09, 4.91mol/L) demonstrate that the average primary particle diameter of theplate-shaped crystalline particles of titanium phosphate changesdepending on the concentration of phosphorus.

FIG. 6 is an SEM image of the titanium phosphate powder obtained inProduction Example 2, and FIG. 7 is an SEM image of the titaniumphosphate powder obtained in Production Example 11 corresponding to thecomparative example. As can be seen from FIGS. 6 and 7, each of theparticles constituting the titanium phosphate powder obtained inProduction Example 2 has a hexagonal plate shape, while each of theparticles constituting the titanium phosphate powder obtained inProduction Example 11 does not have a plate shape but has a rod shape.

The invention claimed is:
 1. A titanium phosphate powder comprisingplate-shaped crystalline particles of titanium phosphate, wherein: theplate-shaped crystalline particles have an average thickness of 0.01 μmor more and 0.048 μm or less; an aspect ratio that is a value obtainedby dividing an average primary particle diameter of the plate-shapedcrystalline particles by the average thickness is 7 or more; and whereinthe plate-shaped crystalline particles have an average primary particlediameter of 0.05 μm or more and 0.24 μm or less.
 2. The titaniumphosphate powder according to claim 1, wherein the average primaryparticle diameter is 0.05 μm or more and 1.5 μm or less.
 3. The titaniumphosphate powder according to claim 2, wherein the plate-shapedcrystalline particles are hexagonal plate-shaped crystalline particles.4. The titanium phosphate powder according to claim 1, wherein theplate-shaped crystalline particles are hexagonal plate-shapedcrystalline particles.
 5. A white pigment for cosmetics, the whitepigment comprising the titanium phosphate powder according to claim 1.6. The titanium phosphate powder of claim 1, wherein the plate-shapedcrystalline particles have an aspect ratio of 9 or more.
 7. The titaniumphosphate powder of claim 1, wherein the plate-shaped crystallineparticles have an aspect ratio of 11 or more.
 8. A titanium phosphatepowder comprising plate-shaped crystalline particles of titaniumphosphate, wherein: the plate-shaped crystalline particles have anaverage thickness of 0.01 μm or more and 0.048 μm or less; an aspectratio that is a value obtained by dividing an average primary particlediameter of the plate-shaped crystalline particles by the averagethickness is 7 or more; and the plate-shaped crystalline particles havean average diameter of 0.05 μm or more and 0.21 μm or less.
 9. Thetitanium phosphate powder according to claim 8, wherein the averageprimary particle diameter is 0.05 μm or more and 1.5 μm or less.
 10. Thetitanium phosphate powder according to claim 9, wherein the plate-shapedcrystalline particles are hexagonal plate-shaped crystalline particles.11. The titanium phosphate powder according to claim 8, wherein theplate-shaped crystalline particles are hexagonal plate-shapedcrystalline particles.
 12. A white pigment for cosmetics, the whitepigment comprising the titanium phosphate powder according to claim 8.13. The titanium phosphate powder according to claim 8, wherein theplate-shaped crystalline particles have an aspect ratio of 9 or more.14. A titanium phosphate powder comprising plate-shaped crystallineparticles of titanium phosphate, wherein: the plate-shaped crystallineparticles have an average thickness of 0.01 μm or more and 0.048 μm orless; an aspect ratio that is a value obtained by dividing an averageprimary particle diameter of the plate-shaped crystalline particles bythe average thickness is 7 or more; and the plate-shaped crystallineparticles have an average diameter of 0.05 μm or more and 0.19 μm orless.
 15. The titanium phosphate powder according to claim 14, whereinthe average primary particle diameter is 0.05 μm or more and 1.5 μm orless.
 16. The titanium phosphate powder according to claim 14, whereinthe plate-shaped crystalline particles are hexagonal plate-shapedcrystalline particles.
 17. A white pigment for cosmetics, the whitepigment comprising the titanium phosphate powder according to claim 14.18. The titanium phosphate powder according to claim 15, wherein theplate-shaped crystalline particles are hexagonal plate-shapedcrystalline particles.
 19. The titanium phosphate powder according toclaim 14, wherein the plate-shaped crystalline particles have an aspectratio of 9 or more.